/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.googlecode.coss.common.utils.xml;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.xml.XMLConstants;
import javax.xml.namespace.QName;
import javax.xml.stream.Location;
import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Namespace;
import javax.xml.stream.events.XMLEvent;
import javax.xml.stream.util.XMLEventConsumer;

import org.xml.sax.Attributes;
import org.xml.sax.Locator;

import com.googlecode.coss.common.utils.lang.StringUtils;
import com.googlecode.coss.common.utils.lang.exception.Assert;

/**
 * SAX <code>ContentHandler</code> that transforms callback calls to
 * <code>XMLEvent</code>s and writes them to a <code>XMLEventConsumer</code>.
 * 
 * @author Arjen Poutsma
 * @see XMLEvent
 * @see XMLEventConsumer
 * @since 3.0
 */
class StaxEventContentHandler extends AbstractStaxContentHandler {

    private final XMLEventFactory  eventFactory;

    private final XMLEventConsumer eventConsumer;

    /**
     * Constructs a new instance of the <code>StaxEventContentHandler</code>
     * that writes to the given <code>XMLEventConsumer</code>. A default
     * <code>XMLEventFactory</code> will be created.
     * 
     * @param consumer the consumer to write events to
     */
    StaxEventContentHandler(XMLEventConsumer consumer) {
        Assert.notNull(consumer, "'consumer' must not be null");
        eventFactory = XMLEventFactory.newInstance();
        eventConsumer = consumer;
    }

    /**
     * Constructs a new instance of the <code>StaxEventContentHandler</code>
     * that uses the given event factory to create events and writes to the
     * given <code>XMLEventConsumer</code>.
     * 
     * @param consumer the consumer to write events to
     * @param factory the factory used to create events
     */
    StaxEventContentHandler(XMLEventConsumer consumer, XMLEventFactory factory) {
        eventFactory = factory;
        eventConsumer = consumer;
    }

    public void setDocumentLocator(final Locator locator) {
        if (locator != null) {
            eventFactory.setLocation(new Location() {

                public int getLineNumber() {
                    return locator.getLineNumber();
                }

                public int getColumnNumber() {
                    return locator.getColumnNumber();
                }

                public int getCharacterOffset() {
                    return -1;
                }

                public String getPublicId() {
                    return locator.getPublicId();
                }

                public String getSystemId() {
                    return locator.getSystemId();
                }
            });
        }
    }

    @Override
    protected void startDocumentInternal() throws XMLStreamException {
        consumeEvent(eventFactory.createStartDocument());
    }

    @Override
    protected void endDocumentInternal() throws XMLStreamException {
        consumeEvent(eventFactory.createEndDocument());
    }

    @Override
    protected void startElementInternal(QName name, Attributes atts,
                                        SimpleNamespaceContext namespaceContext)
            throws XMLStreamException {
        List<Attribute> attributes = getAttributes(atts);
        List<Namespace> namespaces = createNamespaces(namespaceContext);
        consumeEvent(eventFactory.createStartElement(name, attributes.iterator(),
                namespaces != null ? namespaces.iterator() : null));
    }

    @Override
    protected void endElementInternal(QName name, SimpleNamespaceContext namespaceContext)
            throws XMLStreamException {
        List<Namespace> namespaces = createNamespaces(namespaceContext);
        consumeEvent(eventFactory.createEndElement(name, namespaces != null ? namespaces.iterator()
                : null));
    }

    @Override
    protected void charactersInternal(char[] ch, int start, int length) throws XMLStreamException {
        consumeEvent(eventFactory.createCharacters(new String(ch, start, length)));
    }

    @Override
    protected void ignorableWhitespaceInternal(char[] ch, int start, int length)
            throws XMLStreamException {
        consumeEvent(eventFactory.createIgnorableSpace(new String(ch, start, length)));
    }

    @Override
    protected void processingInstructionInternal(String target, String data)
            throws XMLStreamException {
        consumeEvent(eventFactory.createProcessingInstruction(target, data));
    }

    private void consumeEvent(XMLEvent event) throws XMLStreamException {
        eventConsumer.add(event);
    }

    /**
     * Creates and returns a list of <code>NameSpace</code> objects from the
     * <code>NamespaceContext</code>.
     */
    private List<Namespace> createNamespaces(SimpleNamespaceContext namespaceContext) {
        if (namespaceContext == null) {
            return null;
        }

        List<Namespace> namespaces = new ArrayList<Namespace>();
        String defaultNamespaceUri = namespaceContext
                .getNamespaceURI(XMLConstants.DEFAULT_NS_PREFIX);
        if (StringUtils.hasLength(defaultNamespaceUri)) {
            namespaces.add(eventFactory.createNamespace(defaultNamespaceUri));
        }
        for (Iterator<String> iterator = namespaceContext.getBoundPrefixes(); iterator.hasNext();) {
            String prefix = (String) iterator.next();
            String namespaceUri = namespaceContext.getNamespaceURI(prefix);
            namespaces.add(eventFactory.createNamespace(prefix, namespaceUri));
        }
        return namespaces;
    }

    private List<Attribute> getAttributes(Attributes attributes) {
        List<Attribute> list = new ArrayList<Attribute>();
        for (int i = 0; i < attributes.getLength(); i++) {
            QName name = toQName(attributes.getURI(i), attributes.getQName(i));
            if (!("xmlns".equals(name.getLocalPart()) || "xmlns".equals(name.getPrefix()))) {
                list.add(eventFactory.createAttribute(name, attributes.getValue(i)));
            }
        }
        return list;
    }

    //
    // No operation
    //

    @Override
    protected void skippedEntityInternal(String name) throws XMLStreamException {
    }

}
